Does Bluetooth drain your battery?
All wireless technologies need power, but how much is a topic riddled with anecdotes and theories? Despite advancements in Bluetooth technology, it’s still a pretty common belief that you’ll get much more life out of your phone by turning off Bluetooth, Wi-Fi, NFC, and various other features when you’re not using them.
How we tested
To grasp exactly how using Bluetooth impacts battery life, we picked up five different smartphones from 2020. We have the Samsung Galaxy S20 Plus, HUAWEI P40 Pro, ZTE Axon 11, Xiaomi POCO F2 Pro, and realme X3 Superzoom in this test. We ran them through two unique scenarios and monitored the results with our in-house testing software.
The first is a typical daily battery drain scenario designed to determine if turning off Bluetooth actually saves battery. To do this, we performed two sets of tests. The first was done with Bluetooth off and the second with Bluetooth on but idle — i.e., not connected to anything — and then we compared the results. The test itself consists of three cycles — the first features 90 minutes of web browsing followed by 90 minutes of sleep and then 90 more minutes of browsing. Then the phones sleep for 16 hours in the second cycle to give us a good look at idle power draw. The third cycle repeats the first cycle.
We ran five phones through two unique testing scenarios.
Our second set of tests simulates a more demanding Bluetooth-specific use case and should determine how much Bluetooth impacts battery life when you’re actively using it. To simulate this, we monitored video playback for 4 hours straight, as you might do on a long flight. This series consists of a control test with Bluetooth off, Bluetooth on but no connection, and finally, the video audio over Bluetooth using the basic SBC audio codec.
We locked each display brightness to 200 nits to keep the tests fair. Mobile data, NFC, and anything else was also disabled on each handset for all these tests. Except for leaving Wi-Fi on in the first scenario so we can web surf.
We also took averages of the results to give us a better overall look at Bluetooth battery drain. All of the graphs in this article are based on an average based on testing across the five devices mentioned above.
There was a slight difference between the devices we tested. The HUAWEI P40 Pro and POCO F2 Pro saw the most significant difference with Bluetooth on and off — a 3% difference. Meanwhile, the Samsung Galaxy S20 and realme Superzoom recorded slightly less power drain with Bluetooth on. This is likely down to a margin of error, highlighting just how little impact Bluetooth actually has on battery life.
Bluetooth radios turn off during phone sleep, reducing battery drain.
This highlights that modern smartphones put Bluetooth radios to sleep when not in use. They’re only awake and periodically scanning for pairable devices while your smartphone is awake. So, you really don’t need to worry about turning Bluetooth off before you go to bed.
Does using Bluetooth headphones drain battery?
Sony WH 1000MX3 Bluetooth pairing
This is an excellent question and why we conducted these second tests with audio playback as the baseline use case. After all, it’s what most people use Bluetooth for these days.
The results show that playing back audio over Bluetooth consumes essentially the same amount of power as playing back audio over speakers or headphones with Bluetooth turned off. On average, our devices recorded just a 0.2% increase in power consumption when playing back audio over Bluetooth. So, well into the margin of error territory. The Galaxy S20 Plus and POCO F2 Pro recorded no noticeable difference in battery drain over a four-hour listening period.
This is because Bluetooth audio encoding algorithms run efficiently on digital signal processors (DSP) found inside modern smartphones — consuming very little power. At the same time, audio amplifier circuits switch off when playing back audio over Bluetooth. This balances out the power drawn from the Bluetooth wireless chip. The louder you listen, the greater the savings become.
